The present invention relates generally to an electrical interconnection assembly and, more particularly, to such an assembly for interconnecting a submersible pump motor in a downhole to a power cable which extends to the surface of the hole.
While the present invention will be described herein specifically in connection with oil well downhole applications, it will be appreciated that the invention could likewise be used in gas or water wells and in connection with electrical or electronic apparatus other than motor-driven submersible pumps. In oil well downhole applications, the motor for the submersible pump is located below the pump. Thus, the electrical interconnection between the motor and the surface of the downhole must extend upwards past the pump and its accessories to the power cable which leads to the surface of the downhole. This distance may be 12 to 125 feet depending upon the number of stages in the pump. There is very limited space between pump housing and its accessories, and the oil well casing.
In the past, the electrical interconnection assembly for such an application utilized a flat cable with three conductors laid side-by-side, insulated and encased in spirally wrapped monel or phosphor bronze armor. The conductors of the fllat cable assembly were spliced to the electrical leads of the motor for the pump, and the slices were encased in a pothead and potted to provide a seal. In some cases, the conductors have been terminated to a three-pin connector, which is potted or molded, and connected to a mating connector in the motor housing. The opposite end of the conductors have been similarly spliced to the round power cable which extends to the surface of the downhole.
The above described prior art flat cable interconnection assembly has the disadvantage that is flat cable armor is easily subject to damage because of abrasion as it is lowered and withdrawn from the well casing thus causing failure of the electrical connection to the submersible pump motor. Another, more serious cause of failure is leakage due to the difficulty of sealing the armor of the flat cable assembly and electrical termination thereof against up to 5,000 psi crude oil, water, brine, and/or hydrogen sulfide at temperatures up to 310.degree.F. Frequently, due to leakage which occurs in the armor of the flat cable assembly, when the power cable with the flat cable assembly attached thereto is withdrawn from the well and approaches ambient external pressures, the flat cable ruptures or even explodes because of internal pressures developed when the assembly is subjected to the high temperatures and pressures in the lower end of the well. It is the purpose of the present invention to provide an interconnection assembly for submersible motor driven pumps which is less subject to abrasion and rupture than the prior art assemblies discussed hereinabove.